Overview
ISO/TS 15768:2000 - Measurement of liquid velocity in open channels - provides practical guidelines for the design, selection and use of electromagnetic current meters to determine point velocity for open channel flow measurement using the velocity area method. It clarifies how electromagnetic meters differ from rotating-element meters, outlines essential physical characteristics, and gives operational guidance for reliable hydrometric determinations.
Key topics and technical requirements
- Scope and applicability
- Intended for point velocity determination in open channels using the multiple-point sampling technique described in ISO 748.
- Core components
- Typical system comprises: sensing head (probe), means of suspension, control unit, signal cable, and an energy source (usually battery pack).
- Sensing head characteristics
- Contains an electromagnetic coil and one or more pairs of sensing electrodes that detect voltage induced by moving water.
- Variants may have 1–3 electrode pairs (two pairs for horizontal directional sensing; three pairs for vertical and horizontal direction).
- Sensing head construction must resist moisture ingress and surface contamination.
- Electrical and signal considerations
- Signal cable may be integral or detachable; calibration can depend on cable length/type.
- Control unit functions include powering the head, conditioning signals, converting electrical potentials to velocity units, time-averaging, and digital display.
- Environmental and performance constraints
- Devices require sufficient water conductivity; typical minimum conductivity range cited is 30 µS to 100 µS, depending on device and velocity.
- Performance can be affected near the air/water or bed interfaces if the electromagnetic field is disturbed.
- Operational care
- Clean sensing heads after use; avoid oil films (use protective bagging technique if needed).
- Handle connectors carefully (water-resistant connectors, do not disconnect under power).
- Regular maintenance, appropriate suspension method (rod, cable, cableway), and adherence to manufacturer calibration guidance are emphasized.
Practical applications and users
- Who uses ISO/TS 15768
- Hydrometric agencies, water resources engineers, environmental monitoring teams, and instrumentation suppliers selecting or specifying electromagnetic current meters.
- Typical applications
- Open channel flow measurement in rivers, streams, irrigation channels and gauging stations where velocity-area methods are applied.
- Situations requiring direction-aware point velocity sampling and where rotating-element meters are less suitable.
Related standards
- ISO 748 - Velocity-area method for open channel flow (multiple point sampling)
- ISO 772 - Hydrometric vocabulary and symbols
ISO/TS 15768:2000 is a practical, operation-focused technical specification that helps professionals choose and use electromagnetic current meters effectively for accurate open channel flow measurement.